Valve tappet and method of making the same



A. TAUB April 19, 1932.

VALVE TAPPET AND METHOD OF MAKING THE SAME Filed Sept. 1, 1928 wear evenly.

' in the usual manner.

Patented Apr. 19, 1932 UNITED STATES ALEX TAUB, OF DETROIT, MICHIGAN, ASSIGNOR T GENERAL MOTORS CORPORATION,

OF DETROIT, MICHIGAN, A CORPORATION OF DELAWARE VALVE TAPPET AND METHOD OF MAKING THE SAME.

Application filed September 1, 1928. Serial No. 2303;408.

This invention relates to an improved manner of constructing valve tappets of the type such as are commonly used on internal combustion engines.

An object of the invention is to provide a valve tappet having a wear resisting surface at the point where it rests upon the camshaft, and which will be large enough in diameter and of sufiicient length to. furnish a suitable bearing area, but which will at the same time be light in Weight and economical to produce. Such a tappet may be made by welding a chilled cast iron cam-engaging member to a sheet metal body member. The latter may be rolled up out of fiat stock, and a cap welded to it. The parts are so assembled that not only are the cam-engaging member, the body member and the cap welded to each other in a single welding operation,

20 but also the abutting ends of the rolled up body member are welded together by this same operation. A slot is formed in the body member to permit oil to drain out of it, and by locating this slot diagonally in the body, the latter will tend to rotate slightly as it moves up. and down, thus distributing the Other objects and advantages willbe apparent upon referring to the specification and accompanying drawings, in which:

Figure 1 is a fragmentary transverse section through an internal combustion engine, showing my improved valve tappet in connection therewith.

Figure 2 is a vertical section through the tappet. 4

Figure 3 is a the tappet.

Figure 4 is a side View, with parts broken away, of a modified form oftappet.

Figure 5 is a view corresponding to Figure 4 but showing a still different form of tappet.

' The reference numeral indicates the cylinder block casting of an internal combustion horizontal section through engine having a camshaft'12. Located above the camshaft is a push rod 14 which is connected at its upper end to the valve mechanism As the end of the push rod has too small an area to properly provide for wear caused by the impact of the cam, a

member called a tappet and having a relatively large area, is inserted between the lower end of the push rod and the camshaft. In order to function properly, it is usually considered desirable that this tappet member shall be large enough in diameter and long enough to provide a considerable bearing area in the passage in the cylinder block casting in which it is mounted. The tappet must also have a hard wear-resisting surface at the point where it is engaged by the camshaft. One of the most satisfactory materials for this latter purpose has been found to be chilled cast iron. However, if the entire tappet is made of cast iron and is large enough to furnish the proper bearing area, the weight is apt to be so great as to interfere with the proper operation of the engine.

In order to overcome these objections, I have provided a tappet which is composed of a chilled cast iron cam-engaging portion 16 formed with a shoulder 18. Mounted upon this shoulder is a body portion 20 which is rolled up out of a flat sheet of metal 21, as shown in Figure 3, having its ends cut diagonally and so shaped that when it is rolled up into cylindrical form, a narrow diagonal slot 22 will be formed, extending from a point near the bottom of the bodyportion to a point near the top, as shown in Figures 1 and 4. A stamped cap 24 having an opening 26 therein closes the upper end of the body portion. It is obviously much cheaper to form the body portion 20 by rolling it up from flat stock than it would be to use tubing. Also, it is cheaper to use a separate cap than it would be to make the body portion and the cap in one piece by stamping or drawing it.

In order to secure these parts together, a welding current is applied to the cap 24 and to the cam-engaging portion 16, as shown by the wires 28 and 30 in Figure 2. It will be understood thatthe parts are held in any suitable die while being welded and when the welding current is applied, the cap 24 will be welded to the body 20 ,at 32 and the body 20 will be welded to the cam-engaging portion 16 at 34. In addition, while these welds are taking place, the adjacent ends of 1 v has the appearance of the rolled up body portion 20 will be fused together at 36 and 38. It will thus be seen that the welds 32, 34, 36 and 38 will all be performed in a single operation, thus reducing the manufacturing cost. The assembled tappet is then ground on its exterior surface to remove any burns or flash caused by the welding operation and the finished tappet being made of a single piece of metal.

The push rod 14 extends through the opening 26 in the cap and bears against the upper surface 40 of the cam-engaging portlon 16. It is therefore desirable that the surface 40 be ground in order that all of the valve tappets will be of uniform dimensions. By constructin the cam-engaging portion 16 as shown in igures 1 and 2, it readily lends itself to grinding operations since the surface 40 may be ground first in a magnetic chuck, and then by reversing it, the surface 42 may also be ground. It has been found that when the slot 22 is located diagonally in the body portion 20, the latter will tend to rotate a slight amount each time it is moved up and down by the action of the camshaft. This is probably caused by the fact that the film of oil which is present between the tappet and the wall of the passage in which it reciprocates extends into the slot 22, and as the tappet is moved up or down, the body portion tends to rotate in the passage rather than to separate that portion of the oil film which extends into the slot from the oil film which lies between the tappet body portion and the wall of the passage. This is advantageous because it distributes the wear evenly and lengthens the life of the parts.

In engines of the type in which lubricating oil is constantly belng pumped up to the valvemechanism, there is apt to be a flow of oil down the outside of the push rod 14, and the interior of the body portion 20 would soon be filled with oil if some means were not provided to permit it to escape. This would be objectionable since it would increase the weight of the tappet considerably and impair the operation ofthe engine. The slot 22 is therefore provided to permit this oil to escape from the interior of the tappet back into the crankcase.

In the modification shown in Figure 4, the cam-engaging portion 50 is of a slightly different shape and is butt welded to the.

body portion 20. With this construction, it

is not necessary to provide the shoulder 18, but it is slightly more difficult to-grind the upper surface 51. In the form shown in Figure 5, the slot 52 is shown as extending ax1ally with respect to the body portion 20. This form of slot may be used when it-is not considered necessary to have the tappet rotate during operation. It will be readily understood that any combination of'these various parts may be used, since the important feature is the use of a hardened cam-engaging portion with a body portion which is formed from fiat stock to reduce the weight and lower the cost of the tappet. The forms of tappets shown in Figures 4 and 5 may be welded by the same method as described above.

I am aware of the fact that tappets have previously been made having cast cam-engaging portions welded or otherwise secured to tubular steel body portions. But such constructions have not been satisfactory either because the cost was too great, or because they did not'function properly. By constructing the tappet as shown and described, I have overcome these difficulties, and have notonly provided a tappet which is relatively large in size and light in weight, but which is also very simple and cheap to produce.

It is thought from the foregoing taken in connection with the accompanying drawin s, that the construction and operation of the evice will be apparent to those skilled in the art, and that various changes in size, shape, proportion and details of construction may be made without departing from the spirit and scopeof the appended claims.

rised of a cam-engaging ortion, a cyhn rical body portion formed rom a sheet of metal, and a cap, said parts being welded to each other and the abutting ends of the body portion being welded to ether, the sheet of metal from which saif body portion is formed bein of such shape that when the latter isro led into cylindrical form a diagonal slot will be formed extendin substantially from the bottom to the top 0 said body portion, said slot serving to permit oil to escape from the interior of said body portion and also to tend to rotate the latter during operation.

3. Valve mechanism comprising, in combination, a push rod, a cam-engaging portion, asheet metal body portion welded to said cam-engaging portion, and a cap having an opening therein welded to said body portion, said push rod passing through the opening in 'said cap and bearing against the upper surface of said cam-engaging portion.

4. Valve mechanism compr1s1ng,in combi nation, a push rod, a cam-engaging portion, a sheet metal body portion welded to said camengaging portion, a cap having an opening therein welded to said body portion, said push rod passing through the opening in said cap and bearing against the upper surface of said cam-engaging portion, there being an aperture formed in said body portion to permit oil to escape from the latter.

5. The method of forming a composite valve tappet comprised of a cam-engaging portion, a body portion rolled up out of a sheet of metal, and a cap, which consists in applying a welding current to said cam-engaging portion and to said cap and simultaneously welding the cap and the cam engaging portion to said body portion as well as welding together the abuting ends of the rolled up body portion.

6. The method of forming a composite valve tappet which consists in rolling a sheet of metal into a cylindrical body portion, and then welding a cam-engaging portion and a cap to opposite ends of said body portion by applying a welding current to said cap and cam-engaging portion, the abutting ends of said body portion being fused together adjacent the cap and cam-engaging portion as a result of said welding.

In testimony whereof I affix my signature.

ALEX TAUB. 

